1. Field of the Invention
The present invention relates to an implantable electrode lead with a proximal end intended for connection to e.g. a heart stimulator or some other device for electrical stimulation or sensing, primarily in the human body, and a distal end with an electrode head equipped with external anchoring elements, such as tine-like position-fixation elements,
2. Description of the Prior Art
An electrode lead of of the above type can either serve as an implant or be removed from the body after treatment is concluded.
To prevent a recently implanted endocardiac electrode from being dislocated, i.e. from being displaced from its intended position in the heart, it is important for the electrode to be anchored to heart muscle in some suitable fashion. This is especially important the first few days after the implantation, when heart tissue (fibrin) will not have had time to cover or grow around the electrode, thereby achieving natural anchoring of the head.
The endocardiac electrode, arranged on the distal end of its associated electrode lead, is therefore usually equipped with some kind of anchoring means. Conical collars, tines and fins located immediately behind the contact electrode, which is usually a point electrode on the distal end of the electrode lead, are examples of such anchoring means for position-fixation. The purpose of such anchoring means is to cause entanglement or wedging of the endocardiac electrode in the trabeculae in the interior of the heart. Electrodes equipped with tines have proved to be highly effective in achieving reliable anchoring at the desired position in the heart.
When a previously implanted electrode lead has to be removed from the heart for some reason or if its endocardiac electrode requires repositioning in the heart, detaching the electrode from the trabeculae may prove difficult because the electrode's anchoring means have become entangled in the trabeculae or anchored in place by the growth of fibrin onto or around the anchoring means.
Removing the entire electrode lead from the heart or retracting the lead and its contact electrode head a short distance can therefore be much more difficult because of problems in detaching the fixation means from the heart tissue in which they have become entangled or stuck.
In practice, it is often, but not always, possible to detach the end of the electrode lead with the anchoring means from its anchored position in the heart by the application of adequate tractive force.
However, detachment this way can damage the heart tissue, in which the anchoring means are embedded or stuck, to varying degrees.
One electrode lead, known from U.S. Pat. No. 5,179,962, has a distal end section consisting of an electrode head with pin-like fixation means. These fixation means can be switched to/from a retracted, inactive position in which they are completed withdrawn inside the electrode head, or an active position in which they, like times, project at an angle to the rear from the exterior of the electrode head in an area thereof located a short distance from the electrode head's electrode contact surface on the free outer end of the electrode head.
The pin-like position-fixation means are switched between the active and inactive positions with the aid of a stylet, which can move axially inside the electrode lead and electrode head, whose anterior end is attached to a piston-like, sliding holder, inside the electrode head, to which the inner, anterior ends of the anchoring means are attached. The free, posterior parts of the fixation means project to the rear from the holder and then at an angle up through guide holes in a sleeve, made of an electrically insulating material, which encloses the electrode head.
However, this known electrode lead with a retractable, deployable position-fixation means in the electrode head is a constructively complex design, especially as regards the electrode head. A constructively complex electrode lead and electrode head make the design unavoidably expensive.
European Application 0 041 254 discloses an electrode lead which at its distal end contains a harpoon-like component. The harpoon-like element is normally located and held in a longitudinal cavity in the distal end of the electrode lead. The harpoon-like element can be extended from the end of the lead, for instance by means of an internal stylet in the lead, and anchored to the endocavitary wall. Should it be necessary to remove the electrode lead, the harpoon-like element can be pushed entirely out from and released from the electrode lead. The lead then can be removed, the harpoon-like element remaining in the endocavitary wall.
European Application 0 041 254 discloses an electrode lead, which at its distal end is provided with a detachable sleeve. The sleeve is provided with anchoring means in the form of tines. The sleeve is held releasably on the exterior of the distal end, for instance by means of a press fit. In this way the lead can be removed from the heart., leaving the sleeve in the heart.